Heatsink and cooling device

ABSTRACT

A heatsink, which is used with a fluid flow generator that rotates about a central axis extending vertically to generate a flow of fluid, includes a main body section having a top surface facing the fluid flow generator in a vertical direction, and fins that extend upward from the top surface so as to define a plurality of flow passages. Four regions defined by an X axis and a Y axis, which cross each other at an intersection between the central axis and the top surface and extend in an extending direction of the top surface, are referred to as a first region, a second region, a third region, and a fourth region, in order in a direction opposite to a rotation direction of the fluid flow generator. In a plan view from above, the plurality of flow passages form a plurality of fluid paths, each of which has an inlet disposed in at least one of the four regions for the fluid discharged from the fluid flow generator to flow in and an outlet disposed in the first region, and a fluid flow direction changes at an acute angle in the middle in at least one of the fluid paths having the inlet in the fourth region.

TECHNICAL FIELD

The present invention relates to a heatsink and a cooling device.

BACKGROUND ART

Conventionally, there is known a cooling device including a heatsinkthat is thermally connected to a heat generating body, and an electricfan device that blows cooling air to the heatsink (see for examplePatent Document 1).

The heatsink includes a heat receiving section that receives heat from aheat radiating body, a plurality of heat dissipation fins, and coolingair flow paths through which cooling air is blown. The cooling air flowpaths are formed along the heat dissipation fins. The electric fandevice includes a centrifugal impeller. The impeller sucks air anddischarges the sucked air to the cooling air flow paths. The air flowingin the cooling air flow paths works as a main cooling medium thatperforms heat exchange with the heatsink so as to draw heat from theheat generating body. The air that is heated by the heat exchange withthe heatsink is discharged outside from a downstream end of the coolingair flow paths.

LIST OF CITATIONS Patent Literature

Patent Document 1: JP-A-2003-23281

SUMMARY OF THE INVENTION Technical Problem

Now, an outlet direction of the cooling air flow paths may be limited toa particular direction. In this case, a range where the cooling air flowpaths are formed may be limited, and it can be difficult to dissipateheat with the entire heatsink. In addition, if the outlet direction ofthe cooling air flow paths is limited to a particular direction, theremay be generated a cooling air flow path having a long length between aninlet and an outlet, so that the air flow can be decreased.

It is an object of the present invention to provide a technique that canefficiently perform heat dissipation even if a fluid outlet direction islimited to a particular direction.

Means for Solving the Problem

An exemplary heatsink of the present invention is used with a fluid flowgenerator that rotates about a central axis extending vertically togenerate a flow of fluid. The heatsink includes a main body sectionhaving a top surface facing the fluid flow generator in a verticaldirection, and fins that extend upward from the top surface so as todefine a plurality of flow passages. Four regions defined by an X axisand a Y axis, which cross each other at an intersection between thecentral axis and the top surface and extend in an extending direction ofthe top surface are referred to as a first region, a second region, athird region, and a fourth region in order in the opposite direction toa rotation direction of the fluid flow generator. In a plan view fromabove, the plurality of flow passages form a plurality of fluid paths,each of which has an inlet disposed in at least one of the four regionsfor the fluid discharged from the fluid flow generator to flow in and anoutlet disposed in the first region, and a fluid flow direction changesat an acute angle in the middle in at least one of the fluid pathshaving the inlet in the fourth region.

An exemplary cooling device of the present invention includes theheatsink configured as described above and the fluid flow generator.

Advantageous Effects of the Invention

According to the exemplary present invention, it is possible toefficiently perform heat dissipation even if a fluid outlet direction islimited to a particular direction.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view of a cooling device according to an embodiment ofthe present invention.

FIG. 2 is a view after removing a cover from FIG. 1.

FIG. 3 is a vertical cross-sectional view of a fluid flow generatoraccording to the embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view of the cooling deviceaccording to the embodiment of the present invention.

FIG. 5 is a plan view of a heatsink according to the embodiment of thepresent invention.

FIG. 6 is a diagram for describing a main path and a sub-path of theheatsink according to the embodiment of the present invention.

FIG. 7 is a diagram illustrating details of the sub-path according tothe embodiment of the present invention.

FIG. 8 is a diagram for describing a branch section and a joiningsection in the main path of the embodiment of the present invention.

FIG. 9 is a diagram noting a third main path and a fourth main pathillustrated in FIG. 8.

FIG. 10 is a diagram noting a first main path and a second main pathillustrated in FIG. 8.

FIG. 11 is a diagram noting a tenth main path illustrated in FIG. 8.

FIG. 12 is a plan view of the heatsink of a first variation.

FIG. 13 is a diagram illustrating details of the main path in theheatsink of the first variation.

FIG. 14 is a plan view of the heatsink of a second variation.

FIG. 15 is a diagram illustrating details of the main path in theheatsink of the second variation.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an exemplary embodiment of the present invention will bedescribed in detail with reference to the drawings. Note that in thisspecification, a direction parallel to a central axis C illustrated inFIG. 3 of a fluid flow generator 2, which is used with a heatsink 1, isreferred to as an “axial direction”, a direction perpendicular to thecentral axis C is referred to as a “radial direction”, and a directionalong a circle centered at the central axis C is referred to as a“circumferential direction”.

Further in this specification, the axial direction is a verticaldirection, and a side on which the fluid flow generator 2 is disposed tothe heatsink 1 is an upper side, for describing shapes and positionalrelationships of individual sections. However, this definition of thevertical direction is not intended to limit postures of the heatsink andthe cooling device according to the present invention when they areused.

In addition, “upstream” and “downstream” in this specification mean, asa rule, upstream and downstream in a flow direction of the fluid from aninlet 131 to an outlet 132 illustrated in FIG. 2 when the fluid flowgenerator 2 is rotated.

<1. Cooling Device>

FIG. 1 is a plan view of a cooling device 100 according to theembodiment of the present invention. FIG. 1 illustrates the coolingdevice 100 viewed from above. As illustrated in FIG. 1, the coolingdevice 100 includes the heatsink 1 and the fluid flow generator 2. Thecooling device 100 further includes a cover 3.

The heatsink 1 is used with the fluid flow generator 2. The heatsink 1is a heat dissipation member made of a metallic material having goodthermal conductivity, such as aluminum, copper, aluminum alloy, orcopper alloy. FIG. 2 is a view after removing the cover 3 from FIG. 1.In FIG. 2, the fluid flow generator 2 is schematically illustrated. Asillustrated in FIG. 2, the heatsink 1 includes a main body section 10and fins 11. The main body section 10 and the fins 11 are the samemember.

The main body section 10 has a rectangular shape in a plan view fromabove. However, the main body section 10 may have any shape other thanthe rectangular shape, and may have a polygonal shape or the like otherthan the rectangular shape, for example. The main body section 10 has atop surface 10 a facing the fluid flow generator 2 in the verticaldirection. The top surface 10 a extends in a direction perpendicular tothe vertical direction. The top surface 10 a may be a flat surface, ormay be an uneven surface. A peripheral wall 10 b is disposed to extendupward along the peripheral edge of the top surface 10 a except one sideamong four sides.

The fins 11 extend upward from the top surface 10 a. A plurality of fins11 are disposed on the top surface 10 a. In a plan view from above, thefins 11 have various shapes. For instance, in a plan view from above, acertain fin 11 has a linear shape, another fin 11 has a curved shapesuch as an arcuate shape, and still another fin 11 has a shape includinga linear part and a curved part. Note that the fin 11 may have aspot-like shape in a plan view from above. The spot-like fin may have acylindrical shape, a prismatic shape, a spindle shape, or the like, forexample.

The fins 11 define a plurality of flow passages 12. The flow passage 12is a way for fluid to pass. The flow passage 12 is formed between twofins 11. In addition, the flow passage 12 is formed between the fin 11and the peripheral wall 10 b. In this embodiment, the flow passage 12has a groove shape. The fluid flowing in the flow passage 12 contactswith the fins 11 so as to perform heat exchange with them. Specifically,the fluid draws heat from the fins 11. In other words, the fin 11 is aheat dissipation fin.

In FIG. 2, thick broken lines indicate a plurality of fluid paths 13obtained from the plurality of flow passages 12, in a schematic manner.Note that FIG. 2 illustrates only some of the plurality of fluid paths13 obtained from the plurality of flow passages 12. Each of theplurality of fluid paths 13 includes an inlet 131 and an outlet 132. Thefluid path 13 is a way for fluid to flow from one inlet 131 to oneoutlet 132.

The inlet 131 is a place for the fluid discharged from the fluid flowgenerator 2 to flow in. The outlet 132 is a place for discharging tooutside the fluid that has entered through the inlet 131. Here, theoutside means outside of the heatsink 1. In other words, the fluid path13 is a way for the fluid discharged from the fluid flow generator 2 toflow to the outside of the heatsink 1. The fluid passing in each fluidpath 13 performs heat exchange with the fins 11.

As illustrated in FIG. 2, the fluid flow generator 2 generates a fluidflow by rotating about the central axis C extending vertically. Notethat white arrows illustrated in FIG. 2 indicate fluid flows. In thefluid flow generator 2, the direction in which the fluid flows in isdifferent from the direction in which the fluid is discharged. In thisembodiment, the direction in which the fluid flows in is the verticaldirection, while the direction in which the fluid is discharged is adirection perpendicular to the vertical direction. Further in thisembodiment, a rotation direction RD of the fluid flow generator 2 thatrotates around the central axis C is a clockwise direction. However, therotation direction of the fluid flow generator 2 may be acounterclockwise direction. If the rotation direction of the fluid flowgenerator 2 is the counterclockwise direction, the layout and shapes ofthe fins 11 are modified.

Note that the fluid is a gas or a liquid, for example. The gas is air,for example. The liquid is water or liquid coolant, for example. In thisembodiment, the fluid is air.

In addition, the fluid flow generator 2 is a fan or a pump, for example.In this embodiment, the fluid flow generator 2 is a centrifugal fan thatintakes air from the top and discharges the air in a directionperpendicular to the vertical direction. With this structure, when thefluid flow generator 2 is driven, air is taken from the outside into thecooling device 100, and the intake air passes through the fluid paths 13while performing heat exchange, and is discharged to the outside. Withthis air flow, an object to be cooled can be efficiently cooled.

FIG. 3 is a vertical cross-sectional view of the fluid flow generator 2according to the embodiment of the present invention. FIG. 3 alsoillustrates a part of the main body section 10 of the heatsink 1 foreasy understanding. As illustrated in FIG. 3, the fluid flow generator 2includes a motor 20, an impeller 21, and a support part 22.

The motor 20 includes a shaft 201, a stator 202, and a rotor 203. Theshaft 201 extends vertically along the central axis C. The shaft 201 issupported in a rotatable manner by a bearing 204 disposed outside of theshaft 201 in the radial direction. The bearing 204 is housed and held ina bearing holder 205 having a capped cylindrical shape, which issupported by the support part 22. Note that the bearing 204 is a sleevebearing in this embodiment, but it can be other type such as a ballbearing.

The stator 202 has an annular shape around the central axis C. Thestator 202 is disposed outside of the bearing holder 205 in the radialdirection and is fixed to the same. The rotor 203 has a cylindricalshape whose axis is the central axis C. An annular magnet 203 a is fixedto an inner surface of the rotor 203 in the radial direction. The magnet203 a is disposed outside the stator 202 in the radial direction with aspace therebetween. When the stator 202 is supplied with a drivecurrent, a rotation torque is generated between the magnet 203 a and thestator 202. In this way, the rotor 203 rotates with respect to thestator 202.

The impeller 21 includes an impeller cup 211 and a plurality of vanes212. The impeller cup 211 has a bottomed cylindrical shape whose axis isthe central axis C, and is fixed to the shaft 201. The rotor 203 isfixed to an inner surface of the impeller cup 211 in the radialdirection. Therefore, the impeller 21 rotates with rotation of the rotor203.

Each vane 212 extends from an outer surface in the radial direction ofthe impeller cup 211, in a direction separating from the central axis C.The plurality of vanes 212 are arranged with spaces in thecircumferential direction. Note that the direction separating from thecentral axis C may be parallel to the radial direction or may beinclined from the radial direction. When the vanes 212 rotate, air flowis generated.

The support part 22 that supports the motor 20 is fixed to the undersideof the cover 3. Therefore in this embodiment, the fluid flow generator 2is disposed with a space between it and the top surface 10 a of the mainbody section 10 in the vertical direction. However, the support part 22may be united with the cover 3. With this structure, the number ofcomponents can be decreased, and cost can be reduced. In addition, thesupport part 22 may be attached to the top surface 10 a. In other words,the top surface 10 a facing the fluid flow generator 2 in the verticaldirection may be contacted with the same.

As illustrated in FIG. 1, the cover 3 covers the top surface 10 a of themain body section 10 of the heatsink 1. The cover 3 is made of ametallic material having a good thermal conductivity such as iron oriron alloy. The cover 3 is secured to the main body section 10 of theheatsink 1 by means of screws, brazing, or other methods.

Near the center of the cover 3, a circular cover aperture 3 a is formedso as to penetrate the same in the vertical direction. The fluid flowgenerator 2 attached to the underside of the cover 3 is exposed to theoutside of the cooling device 100 through the cover aperture 3 a. Whenthe fluid flow generator 2 is driven, the fluid flows in from theoutside of the cooling device 100 through the cover aperture 3 a. Inaddition, when the fluid flow generator 2 is driven, the sucked-in fluidpasses through the fluid paths 13 formed in the heatsink 1 and isdischarged to the outside of the cooling device 100 through the partwithout the peripheral wall 10 b.

FIG. 4 is a schematic cross-sectional view of the cooling device 100according to the embodiment of the present invention. As illustrated inFIG. 4, the main body section 10 has a cooled body housing section 101for housing a cooled body on an underside 10 c. The cooled body is theobject to be cooled, and in the example illustrated in FIG. 4, itcorresponds to a heat generating body 4 and a substrate 5 on which theheat generating body 4 is mounted. As the heat generating body 4, thereis a heat generating element such as a semiconductor chip or atransistor.

In this embodiment, the cooled body housing section 101 includes anelement housing section 101 a and a substrate housing section 101 b.However, it may be configured to include only one of the element housingsection 101 a and the substrate housing section 101 b. The elementhousing section 101 a is a recess dented upward on the underside 10 c ofthe main body section 10, so as to house at least a part of the heatgenerating element as the heat generating body 4. It is preferred thatthe heat generating body 4 housed in the element housing section 101 acontacts with the main body section 10. Note that it is sufficient thatthe heat generating body 4 thermally contacts with the main body section10, and there may be thermal grease between the heat generating body 4and the main body section 10, for example. The substrate housing section101 b is a section for housing the substrate 5, and it is preferred thatthe substrate 5 housed in the substrate housing section 101 b isthermally contacted with the main body section 10.

When the fluid flow generator 2 is driven, the fluid passing through theplurality of fluid paths 13 performs heat exchange with the heatsink 1so as to draw heat from the cooled body. In this way, the cooled body iscooled. The fluid heated by heat exchange with the heatsink 1 passesthrough the outlet 132 of the fluid path 13 and is discharged outside ofthe cooling device 100. In this embodiment, a wide area of the heatsink1 that is used with the fluid flow generator 2 can be cooled by thefluid, and hence the cooled body can be efficiently cooled. Further inthis embodiment, as the cooled body housing section 101 for housing thecooled body is formed in the underside of the heatsink 1 whose wide areacan be cooled, restrictions about the layout of the cooled body can bereduced.

<2. Details of Heatsink>

(2-1. Outline of Fluid Path)

FIG. 5 is a plan view of the heatsink 1 according to the embodiment ofthe present invention. FIG. 5 illustrates the heatsink 1 viewed fromabove. Broken line arrows in FIG. 5 indicate fluid flows. In thisembodiment, the fluid flow is air flow or wind. Also in FIG. 5,similarly to FIG. 2, some of the plurality of fluid paths 13 obtainedfrom the plurality of flow passages 12 are schematically shown in thickbroken lines. A white arrow RD in FIG. 5 indicates the rotationdirection of the fluid flow generator 2.

In FIG. 5, four regions R1, R2, R3, and R4 defined by an X axis and a Yaxis, which cross each other at an intersection CP between the centralaxis C and the top surface 10 a and extend in an extending direction ofthe top surface 10 a, are referred to as a first region R1, a secondregion R2, a third region R3, and a fourth region R4, in order in adirection opposite to the rotation direction RD of the fluid flowgenerator 2. The extending direction of the top surface 10 a is adirection perpendicular to the vertical direction. The rotationdirection RD is the clockwise direction, while the direction opposite tothe rotation direction RD is the counterclockwise direction.

Note that in this embodiment, the X axis is orthogonal to the Y axis.However, the X axis may not be orthogonal to the Y axis. Further in thisembodiment, the X axis and the Y axis do not equally divide the topsurface 10 a of the main body section 10 into four regions. However, theX axis and the Y axis may equally divide the top surface 10 a of themain body section 10.

As illustrated in FIG. 5, in a plan view from above, the inlet 131 ofeach fluid path 13 is disposed in at least one of the four regions R1,R2, R3, and R4. Each inlet 131 may be disposed in only one of the fourregions R1, R2, R3, and R4 or disposed over a plurality of regions.

In this embodiment, a first inlet 131 a, a second inlet 131 b, a thirdinlet 131 c, a fourth inlet 131 d, a fifth inlet 131 e, a sixth inlet131 f, a seventh inlet 131 g, an eighth inlet 131 h, a ninth inlet 131i, a tenth inlet 131 j, an eleventh inlet 131 k, and a twelfth inlet 131l are disposed in order from the first region R1 in the rotationdirection RD of the fluid flow generator 2.

The first inlet 131 a and the second inlet 131 b are disposed in thefirst region R1. The third inlet 131 c, the fourth inlet 131 d, thefifth inlet 131 e, and the sixth inlet 131 f are disposed in the fourthregion R4. The seventh inlet 131 g and the eighth inlet 131 h aredisposed in the third region R3. The ninth inlet 131 i is disposed overthe third region R3 and the second region R2. The tenth inlet 131 j, theeleventh inlet 131 k, and the twelfth inlet 131 l are disposed in thesecond region R2.

As illustrated in FIG. 5, in a plan view from above, the outlet 132 ofeach fluid path 13 is disposed in the first region R1. Specifically, allthe outlets 132 of the plurality of fluid paths 13 are disposed in thefirst region R1. In other words, in the heatsink 1 of this embodiment,the outlets 132 of the fluid paths 13 are disposed in a particulardirection in a biased manner.

In this embodiment, in the first region R1, a first outlet 132 a, asecond outlet 132 b, a third outlet 132 c, a fourth outlet 132 d, afifth outlet 132 e, a sixth outlet 132 f, a seventh outlet 132 g, aneighth outlet 132 h, a ninth outlet 132 i, a tenth outlet 132 j, and aneleventh outlet 132 k are disposed, in order from upstream to downstreamof the rotation direction RD of the fluid flow generator 2.

Note that in this embodiment, only one fluid path 13 is obtained fromone inlet 131 in one structure, and a plurality of fluid paths 13 areobtained from one inlet 131 in another structure, which are mixed.However, without limiting to these mixed structures, only one of theformer and latter structures may be disposed, for example. In the formerstructure, the inlet 131 and the outlet 132 always have a one-to-onerelationship. The latter structure may include a structure in which theplurality of fluid paths 13 share the same outlet 132, for example. Inaddition, the latter structure may include a structure in which theplurality of fluid paths 13 have different outlets 132.

Specific examples are given with reference to FIG. 5. For example, as tothe seventh inlet 131 g disposed in the third region R3, only one fluidpath 13 from the seventh inlet 131 g to the third outlet 132 c isobtained. As to the sixth inlet 131 f disposed in the fourth region R4,total three fluid paths 13 are obtained, which include the fluid path 13from the sixth inlet 131 f to the first outlet 132 a, and the two fluidpats 13 from the sixth inlet 131 f to the second outlet 132 b.

Note that the first inlet 131 a, the second inlet 131 b, the third inlet131 c, the fourth inlet 131 d, the fifth inlet 131 e, the sixth inlet131 f, the tenth inlet 131 j, and the eleventh inlet 131 k are shared bya plurality of fluid paths 13. In addition, the first outlet 132 a, thesecond outlet 132 b, the seventh outlet 132 g, the eighth outlet 132 h,the tenth outlet 132 j, and the eleventh outlet 132 k are shared by aplurality of fluid paths 13.

Further in this embodiment, the fins 11 include Y-shaped fins 11 a and11 b. As the Y-shaped fins 11 a and 11 b are disposed on the top surface10 a, stiffness of the heatsink 1 can be improved. In addition, usingthe Y-shaped fin 11 a, 11 b for constituting the flow passage 12, thefluid can be easily guided to different directions. Although twoY-shaped fins 11 a and 11 b are used in this embodiment, the number ofthe Y-shaped fins may not be two. The Y-shaped fin 11 a, one of twoY-shaped fins, is disposed over the third region R3 and the fourthregion R4. The Y-shaped fin 11 b, the other of two Y-shaped fins, isdisposed over the first region R1 and the fourth region R4.

As to the heatsink 1, in a plan view from above, in at least one of thefluid paths 13 having the inlet 131 in the fourth region R4, the fluidflow direction changes at an acute angle in the middle thereof. Asillustrated in FIG. 5, in this embodiment, four inlets 131 including thethird inlet 131 c, the fourth inlet 131 d, the fifth inlet 131 e, andthe sixth inlet 131 f are disposed in the fourth region R4. Among thefour inlets 131, the third inlet 131 c is the inlet 131 of the fluidpath 13, and the fourth inlet 131 d is the inlet 131 of the fluid path13, in both of which the fluid flow direction changes at an acute anglein the middle thereof.

The middle means a position or a region between the inlet 131 and theoutlet 132. In other words, in at least one of the fluid paths 13 havingthe inlet 131 in the fourth region R4, the fluid flow direction changesat an acute angle on downstream of the inlet 131. In this embodiment,the fluid flow direction does not change at an acute angle at the inlet131. In addition, that the fluid flow direction changes at an acuteangle means that an angle between the flow direction of the fluid onupstream of a position or a small region as a boundary and that ondownstream of the same is an acute angle. The small region is a regionhaving a length of one fifth or less of the entire length of the fluidpath 13 in each fluid path 13. The small region is preferably a regionhaving a length of one eighth or less of the entire length of the fluidpath 13 in each fluid path 13.

Here, as a comparative example of this embodiment, a case is consideredwhere extending directions of the fluid paths 13 are only directionsalong the rotation direction RD of the fluid flow generator 2. In thiscase, the fluid path having the inlet 131 in the fourth region R4 isconsidered to cause bad fluid flow because the distance to the outlet132 disposed in the first region R1 is increased. In other words, thefluid flowing in this fluid path is considered to have lowercontribution to cooling effect.

In contrast, with the structure of this embodiment, at least one of thefluid paths 13 having the inlet 131 in the fourth region R4 is formed soas to change the fluid flow direction at an acute angle. Therefore, inat least one of the fluid paths 13 having the inlet 131 in the fourthregion R4, the distance to the outlet 132 can be decreased so that goodfluid flow can be obtained. In other words, with this structure, thefluid flowing in the fluid path 13 having the inlet 131 in the fourthregion R4 can contribute more to the cooling effect. In addition, withthis structure, the fluid paths 13 can be formed in a large area of thefourth region R4 that can be a dead space in a conventional structure,and the area for the fluid to flow can be increased so that coolingefficiency can be improved. In addition, in this structure, the fluidflow direction changes at an acute angle on downstream of the inlet 131,and the fluid flow direction can be changed more efficiently than thestructure in which the fluid flow direction is changed rapidly at theinlet of the path.

(2-2. Main Path and Sub-Path)

FIG. 6 is a diagram for describing a main path 13M and a sub-path 13S ofthe heatsink 1 according to the embodiment of the present invention.Similarly to FIG. 5, FIG. 6 is a plan view of the heatsink 1 viewed fromabove. In FIG. 6, thick solid lines are added for roughly grasping typesof the fluid paths 13, and they are not necessarily intended to beboundary lines for separating types of the fluid paths 13. In addition,the main path 13M, the sub-path 13S, and an auxiliary path 13A shown bythick broken lines in FIG. 6 are merely examples of a plurality of thepaths.

At least some of the plurality of fluid paths 13 formed in the topsurface 10 a of the main body section 10 are classified into the mainpaths 13M and the sub-paths 13S. In this embodiment, some of theplurality of fluid paths 13 are classified into the main paths 13M andthe sub-paths 13S. Specifically, the plurality of fluid paths 13 areclassified into the main paths 13M, the sub-paths 13S, and the auxiliarypaths 13A.

The main path 13M is the fluid path 13 in which the fluid flows in thesame direction as the rotation direction RD of the fluid flow generator2. That the fluid flows in the same direction as the rotation directionRD means that, with respect to an imaginary line connecting the centralaxis C and a noted point in the fluid path 13 in a plan view from above,the fluid flowing at the noted point flows with an inclination in thesame direction as the rotation direction RD of the fluid flow generator2. In the main path 13M, the fluid flows in the same direction as therotation direction RD of the fluid flow generator 2 in the entire rangeor in a substantially entire range. For instance, when the fluid flowdirection is changed for adjusting the fluid discharge direction nearthe outlet 132, it may be a substantially entire range. In thisembodiment, in the main path 13M, the fluid flows in the same directionas the rotation direction RD of the fluid flow generator 2 in the entirerange.

In this embodiment, the main path 13M is the fluid path 13 that has theinlet 131 in the fourth region R4, the third region R3, or the secondregion R2, and has the outlet 132 that is one of the first outlet 132 a,the second outlet 132 b, the third outlet 132 c, the fourth outlet 132d, the fifth outlet 132 e, the sixth outlet 132 f, and the seventhoutlet 132 g (see FIG. 5).

As a preferred configuration, in this embodiment, the main paths 13Minclude at least one of the fluid paths 13 having the inlet 131 in thethird region R3. Specifically, the main paths 13M include a plurality ofthe fluid paths 13 having the inlet 131, that is the seventh inlet 131g, the eighth inlet 131 h, or the ninth inlet 131 i, disposed in thethird region R3 at least partially. In this way, by means of the mainpaths 13M, it is possible to cool the large area including not only thefirst region R1 and the second region R2 but also the third region R3.

The sub-path 13S is the fluid path 13 having a part where the fluid flowdirection is switched at an acute angle from the rotation direction ofthe fluid flow generator 2 to the opposite direction. That the fluidflows in the opposite direction to the rotation direction RD means that,with respect to the imaginary line connecting the central axis C and anoted point in the fluid path 13 in a plan view from above, the fluidflowing at the noted point flows with an inclination in the oppositedirection to the rotation direction RD of the fluid flow generator 2.The part where the fluid flow direction is switched at an acute angle islocated downstream of the inlet 131. The part where the fluid flowdirection is switched at an acute angle is a position or a small regionin the fluid path 13.

In this embodiment, the sub-path 13S is the fluid path 13 having theinlet 131 in the fourth region R4 or the first region R1 and the outlet132 that is the tenth outlet 132 j or the eleventh outlet 132 k (seeFIG. 5). With this structure, using the main path 13M, a large area ofthe heatsink 1 can be cooled. Further, disposing the sub-path 13S in thearea where the main path 13M is hardly disposed in the heatsink 1, alarger area of the heatsink 1 can be cooled.

As a preferred configuration, in this embodiment, the sub-paths 13Sinclude at least one of the fluid paths 13 having the inlet 131 in thefirst region R1, in addition to at least one of the fluid paths 13having the inlet 131 in the fourth region R4. Specifically, thesub-paths 13S include a plurality of the fluid paths 13 having the inlet131 that is the third inlet 131 c or the fourth inlet 131 d located inthe fourth region R4 (see FIG. 5). In addition, the sub-paths 13Sinclude a plurality of the fluid paths 13 having the inlet 131 that isthe first inlet 131 a or the second inlet 131 b located in the firstregion R1 (see FIG. 5). With this structure, it is possible to send thefluid to the fourth region R4 also from the first region R1, and hencethe fourth region R4 can be efficiently cooled though it can hardly becooled by the main path 13M.

The auxiliary path 13A is the fluid path 13 having a part where thefluid flow direction is switched from the rotation direction RD of thefluid flow generator 2 to the opposite direction. However, in theauxiliary path 13A, the fluid flow direction is not switched at an acuteangle. In other words, the auxiliary path 13A is different from the mainpath 13M or the sub-path 13S. The part where the fluid flow direction isswitched from the rotation direction RD to the opposite direction islocated downstream of the inlet 131.

In this embodiment, the auxiliary path 13A is the fluid path 13 havingthe inlet 131 in the second region R2 and the outlet 132 that is theeighth outlet 132 h or the ninth outlet 132 i (see FIG. 5). Note thatthe auxiliary path 13A may not be disposed. However, by disposing theauxiliary path 13A, a large area of the heatsink 1 can be cooled.

As described above, in this embodiment, there is the Y-shaped fin 11 bdisposed over the first region R1 and the fourth region R4. The Y-shapedfin 11 b includes a part extending linearly to the outlet 132 in thefirst region R1. As the Y-shaped fin 11 b is disposed, the sub-path 13Scan be formed differently from other type of path. In this embodiment,the other type of path is the auxiliary path 13A. Note that if it is notnecessary to be completely different from other type of path, a V-shapedfin may be disposed instead of the Y-shaped fin 11 b. If the Y-shapedfin 11 b in this embodiment is replaced with the V-shaped fin, a part ofthe sub-path 13S and a part of the auxiliary path 13A are merged.

Further in this embodiment, in the Y-shaped fin 11 b disposed over thefirst region R1 and the fourth region R4, the part extending linearly tothe outlet 132 is disposed biased to the fourth region R4 from thecenter in the arrangement direction of the plurality of outlets 132.However, this disposition may be modified. For instance, the partextending linearly to the outlet 132 may be disposed at the center inthe arrangement direction of the plurality of outlets 132. In this case,the auxiliary path 13A may not be disposed.

(2-3. Details of Sub-Path)

FIG. 7 is a diagram illustrating details of the sub-path 13S accordingto the embodiment of the present invention. FIG. 7 is an enlarged viewof a part of the heatsink 1 viewed from above. At least some of theplurality of sub-paths 13S have a sub-path joining section 133 forjoining another sub-path 13S. In this embodiment, each of the pluralityof sub-paths 13S has the sub-path joining section 133 for joininganother sub-path 13S.

In each sub-path 13S, the sub-path joining section 133 is disposeddownstream of the inlet 131. The sub-path joining section 133 is formedby breaking the fin 11 defining the flow passage 12 before reaching theoutlet 132 from the inlet 131. In a plan view from above, the sub-pathjoining section 133 is an end on the downstream side of the fin 11broken before reaching the outlet 132. In the sub-path joining section133, the flow rate is increased because the fluids are collected fromthe plurality of fluid paths 13. Therefore, it is possible to preventstagnation of fluid flow in the sub-path 13S having a part where thefluid flow is switched at an acute angle.

As illustrated in FIG. 7, in this embodiment, there is a joining region30 where the fluids after passing through the sub-path joining sections133 are collected. On upstream of the joining region 30, there are afirst pre-joining flow passage 12 a, a second pre-joining flow passage12 b, a third pre-joining flow passage 12 c, and a fourth pre-joiningflow passage 12 d, in order in the rotation direction RD. On downstreamof the joining region 30, there are a first post-joining flow passage 12e and a second post-joining flow passage 12 f in order in the rotationdirection RD. In other words, the number of the flow passages 12 afterjoining is decreased from that before joining. In this way, the flowrate becomes short so that stagnation of fluid flow can be prevented.

In addition, the first pre-joining flow passage 12 a and the secondpre-joining flow passage 12 b join each other before they join the thirdpre-joining flow passage 12 c and the fourth pre-joining flow passage 12d. In other words, the fluid flowing in the first pre-joining flowpassage 12 a joins the fluid flowing in the second pre-joining flowpassage 12 b, and afterward joins the fluids flowing in the thirdpre-joining flow passage 12 c and the fourth pre-joining flow passage 12d. In addition, the fluid flowing in the second pre-joining flow passage12 b joins the fluid flowing in the first pre-joining flow passage 12 a,and afterward joins the fluids flowing in the third pre-joining flowpassage 12 c and the fourth pre-joining flow passage 12 d.

However, without limiting to this, the fluids flowing in the firstpre-joining flow passage 12 a, the second pre-joining flow passage 12 b,the third pre-joining flow passage 12 c, and the fourth pre-joining flowpassage 12 d may join at one time, for example. In this embodiment, thefirst pre-joining flow passage 12 a has a step where the verticaldirection height of the flow passage is increased from upstream todownstream. The step is formed due to a component disposed on theunderside 10 c of the main body section 10, for example. Because of thisstep, the fluid flow can be decreased in the first pre-joining flowpassage 12 a. In this embodiment, as the first pre-joining flow passage12 a and the second pre-joining flow passage 12 b join each otherearlier, the above-mentioned decrease in the fluid flow can beprevented.

(2-4. Details of Main Path)

FIG. 8 is a diagram for describing branch sections 134 a to 134 d andjoining sections 135 a to 135 c in the main paths 13M of the embodimentof the present invention. FIG. 8 illustrates the heatsink 1 viewed fromabove. In FIG. 8, thick broken lines indicate the main paths 13M.

As illustrated in FIG. 8, the main paths 13M include a first main path13M1, a second main path 13M2, a third main path 13M3, a fourth mainpath 13M4, a fifth main path 13M5, a sixth main path 13M6, a seventhmain path 13M7, an eighth main path 13M8, a ninth main path 13M9, atenth main path 13M10, and an eleventh main path 13M11.

The first main path 13M1 is the fluid path from the fifth inlet 131 e tothe first outlet 132 a. The second main path 13M2 is the fluid path fromthe fifth inlet 131 e to the second outlet 132 b. The third main path13M3 is the fluid path from the sixth inlet 131 f to the first outlet132 a. The fourth main path 13M4 is one of the two fluid paths from thesixth inlet 131 f to the second outlet 132 b. The fifth main path 13M5is the other of the two fluid paths from the sixth inlet 131 f to thesecond outlet 132 b. In a plan view from above, the fourth main path13M4 is located outside of the fifth main path 13M5 with respect to theintersection CP. Note that details of the inlets 131 and the outlets 132are illustrated in FIG. 5.

The sixth main path 13M6 is the fluid path from the seventh inlet 131 gto the third outlet 132 c. The seventh main path 13M7 is the fluid pathfrom the eighth inlet 131 h to the fourth outlet 132 d. The eighth mainpath 13M8 is the fluid path from the ninth inlet 131 i to the fifthoutlet 132 e. The ninth main path 13M9 is the fluid path from the tenthinlet 131 j to the sixth outlet 132 f. The tenth main path 13M10 is thefluid path from the tenth inlet 131 j to the seventh outlet 132 g. Theeleventh main path 13M11 is the fluid path from the eleventh inlet 131 kto the seventh outlet 132 g. Note that details of the inlets 131 and theoutlets 132 are illustrated in FIG. 5.

At least some of the plurality of main paths 13M have at least one ofthe branch section and the joining section. At the branch section, thefluid path 13 blanches into at least two. At the joining section, atleast two fluid paths 13 join together. The branch section and thejoining section are formed at ends of the fin 11 constituting the flowpassage 12, in a plan view from above.

As illustrated in FIG. 8, in this embodiment, some of the plurality ofmain paths 13M have at least one of the branch section 134 a to 134 dand the joining section 135 a to 135 c. With reference to FIGS. 9 to 11,details of the branch sections 134 a to 134 d and the joining sections135 a to 135 c are described.

FIG. 9 is a diagram noting the third main path 13M3 and the fourth mainpath 13M4 illustrated in FIG. 8. As illustrated in FIG. 9, the thirdmain path 13M3 has the two branch sections 134 a and 134 b and the onejoining section 135 a. The fourth main path 13M4 has the two branchsections 134 a and 134 b and the two joining sections 135 a and 135 b.

The third main path 13M3 and the fourth main path 13M4 have the branchsection 134 a for branching from the fifth main path 13M5 on downstreamof the sixth inlet 131 f. In other words, at least one of the pluralityof fluid paths 13 has a first branch section 1341 for branching from thefirst fluid path 13 a on downstream of the inlet 131. In the exampleillustrated in FIG. 9, the fifth main path 13M5 is the first fluid path13 a, and the number of the first fluid paths 13 a is one. However, thenumber of the first fluid paths 13 a may be plural. In addition, in theexample illustrated in FIG. 9, the branch section 134 a is the firstbranch section 1341.

The third main path 13M3 and the fourth main path 13M4 have the joiningsection 135 a for joining the first main path 13M1 and the second mainpath 13M2 each having the fifth inlet 131 e as the inlet 131, ondownstream of the branch section 134 a. In other words, at least one ofthe plurality of fluid paths 13 has a first joining section 1351 forjoining the second fluid path 13 b having another inlet 131, ondownstream of the first branch section 1341. In the example illustratedin FIG. 9, the first main path 13M1 and the second main path 13M2 arethe second fluid paths 13 b, and the number of the second fluid paths 13b is two. However, the number of the second fluid paths 13 b may be oneor more than two. In addition, in the example illustrated in FIG. 9, thejoining section 135 a is the first joining section 1351.

According to this embodiment, the first branch section 1341 can increasethe number of the flow passages 12 defined by the fins 11 so thatcooling efficiency can be improved. According to this embodiment, whileimproving the cooling efficiency, the first joining section 1351disposed on downstream of the first branch section 1341 can preventstagnation of fluid flow due to the branching of the fluid path 13.

In addition, the third main path 13M3 and the fourth main path 13M4further include the branch section 134 b for branching the fluid path 13on downstream of the joining section 135 a. In other words, a part ofthe plurality of fluid paths 13 includes a second branch section 1342for branching the fluid path 13 on downstream of the first joiningsection 1351. In the example illustrated in FIG. 9, the branch section134 b is the second branch section 1342. The second branch section 1342branches the fluid path 13. Specifically, it is branched into the thirdmain path 13M3 and the fourth main path 13M4. In this embodiment, thenumber of the second branch section 1342 is one, but it may be plural.

With this structure, by disposing the second branch section 1342 forbranching the fluid path 13, the area in which the fluid flows can beincreased. In this way, the cooling region of the heatsink 1 can beincreased. However, the second branch section 1342 may not be disposed.In this case, for example, the first main path 13M1 and the third mainpath 13M3 may not be disposed.

In addition, the third main path 13M3 further includes, in addition tothe joining section 135 a, the joining section 135 b for joining thefifth main path 13M5 that has branched at the branch section 134 a. Asdescribed above, in the example illustrated in FIG. 9, the branchsection 134 a is the first branch section 1341, the joining section 135a is the first joining section 1351, and the fifth main path 13M5 is thefirst fluid path 13 a. In other words, a part of the plurality of fluidpaths 13 further includes, in addition to the first joining section1351, the second joining section 1352 for joining the first fluid path13 a that has branched at the first branch section 1341. In the exampleillustrated in FIG. 9, the joining section 135 b is the second joiningsection 1352. With this structure, the second joining section 1352different from the first joining section 1351 can also preventstagnation of fluid flow.

FIG. 10 is a diagram noting the first main path 13M1 and the second mainpath 13M2 illustrated in FIG. 8. As illustrated in FIG. 10, the firstmain path 13M1 includes the one branch section 134 b and the one joiningsection 135 a. The second main path 13M2 includes the one branch section134 b and the two joining sections 135 a and 135 b.

In details, the first main path 13M1 and the second main path 13M2 jointhe third main path 13M3 and the fourth main path 13M4 at the joiningsection 135 a. The first main path 13M1 and the second main path 13M2branch from each other at the branch section 134 b. The second main path13M2 joins the fifth main path 13M5 at the joining section 135 b.

Here, the second main path 13M2 is noted. The second main path 13M2 hasthe branch section 134 b for branching from the first main path 13M1 ondownstream of the fifth inlet 131 e. In other words, the branch section134 b can be regarded as the first branch section 1341 described above.The branch section 134 b has functions as the first branch section 1341and the second branch section 1342. Note that in the example illustratedin FIG. 10, the first main path 13M1 is the first fluid path 13 adescribed above.

In addition, the second main path 13M2 includes the joining section 135b for joining the fifth main path 13M5 having the sixth inlet 131 f asthe inlet 131, on downstream of the branch section 134 b working as thefirst branch section 1341. In other words, the joining section 135 b canbe regarded as the first joining section 1351. The joining section 135 bhas functions as the first joining section 1351 and the second joiningsection 1352. Note that in this case, the fifth main path 13M5 is thesecond fluid path 13 b described above.

In this embodiment, at least one of the main paths 13M has the firstbranch section 1341 and the first joining section 1351. With thisstructure, even if a lot of the inlets 131 for the main paths 13M, inwhich the fluid path 13 tends to be long, cannot be disposed for limitedspace, for example, the area where the main paths 13M are disposed canbe increased while preventing stagnation of fluid flow, by disposing thefirst branch section 1341 and the first joining section 1351. As aresult, cooling efficiency of the heatsink 1 can be improved.

Note that the first branch section 1341 and the first joining section1351 may be disposed in the sub-path 13S and the auxiliary path 13A.

Further in this embodiment, among the plurality of fluid paths 13, atleast one of long distance paths 13LD, which pass through the thirdregion R3 and the second region R2 between the inlet 131 and the outlet132, has the first branch section 1341 and the first joining section1351. Specifically, the long distance path 13LD is the fluid path 13that passes at least the third region R3, the second region R2, and thefirst region RE The long distance path 13LD may be the fluid path 13that passes through the fourth region R4, the third region R3, thesecond region R2, and the first region RE

In this embodiment, the second main path 13M2, the third main path 13M3,and the fourth main path 13M4 have the first branch section 1341 and thefirst joining section 1351. The second main path 13M2, the third mainpath 13M3, and the fourth main path 13M4 are long distance paths 13LDthat pass through the fourth region R4, the third region R3, the secondregion R2, and the first region R1.

As to the fluid flowing in the rotation direction RD of the fluid flowgenerator 2, the distance from the inlet 131 to the outlet 132 becomeslong in the long distance path 13LD, and hence the fluid flow tends tostagnate. Therefore, as conventional common sense, it is not easy todispose the fin 11 in the middle of the fluid path 13 to form the branchsection for the long distance path 13LD. However, in this embodiment,the first joining section 1351 is disposed for compensating stagnationof fluid flow that can be caused by disposing the first branch section1341. Therefore, also for the long distance path 13LD, the fin 11constituting the branch section can be disposed in the middle, and hencecooling efficiency can be improved.

Note that the first branch section 1341 and the first joining section1351 may be disposed also in a short distance path 13SD that passesthrough only the second region R2 and the first region R1, or only thefirst region R1. FIG. 11 is a diagram noting the tenth main path 13M10illustrated in FIG. 8. As illustrated in FIG. 11, in this embodiment,the tenth main path 13M10 as the short distance path 13SD has the firstbranch section 1341 and the first joining section 1351. Specifically,the branch section 134 c is the first branch section 1341. The ninthmain path 13M9 is the first fluid path 13 a. The joining section 135 cis the first joining section 1351. One of the fluid paths 13 having theeleventh inlet 134 k (see FIG. 5) as the inlet is the second fluid path13 b. Note that the branch section 134 d is the second branch section1342 disposed on downstream of the first joining section 1351.

Further in this embodiment, as to the inlets 131 and the outlets 132that are shared among the plurality of fluid paths 13, when the numberis each counted as one, the number of the outlets 132 is the same asthat of the inlets 131 for the long distance path 13LD. Specifically,the long distance path 13LD has the inlets 131 including the fifth inlet131 e, the sixth inlet 131 f, the seventh inlet 131 g, the eighth inlet131 h, and the ninth inlet 131 i (see FIG. 5), and the number of theinlets 131 of the long distance path 13LD is five. The long distancepath 13LD has the outlets 132 including the first outlet 132 a, thesecond outlet 132 b, the third outlet 132 c, the fourth outlet 132 d,and the fifth outlet 132 e (see FIG. 5), and the number of the outlets132 of the long distance path 13LD is also five. With this structure, inthe long distance path 13LD, unnecessary increase of branching of thepath is prevented, and stagnation of fluid flow can be prevented.

Further in this embodiment, at least one of the long distance paths 13LDhas the inlet 131 in the fourth region R4. Specifically, the first mainpath 13M1, the second main path 13M2, the third main path 13M3, thefourth main path 13M4, and the fifth main path 13M5, which are some ofthe long distance paths 13LD, have the inlet 131 in the fourth regionR4. In this way, the fourth region R4 can be used positively as a returnpath for the fluid, and hence cooling efficiency can be improved.

<3. Variation>

(3-1. First Variation)

FIG. 12 is a plan view of a heatsink 1α of a first variation. FIG. 12illustrates the heatsink 1α viewed from above. Similarly to theembodiment described above, the heatsink 1α of the first variation alsohas fins 11α for defining a plurality of flow passages 12α on a topsurface 10 aα of a main body section 10α. A plurality of fluid paths 13αare obtained from the plurality of flow passages 12α. The plurality offluid paths 13α are classified into main paths 13Mα, sub-paths 13Sα, andauxiliary paths 13Aα. A plurality of the main paths 13Mα, a plurality ofthe sub-paths 13Sα, and a plurality of the auxiliary paths 13Aα aredisposed. Note that only some of the plurality of fluid paths are shownby thick lines in FIG. 12.

Also in the first variation, in the main paths 13Mα, the fluid flows inthe same direction as the rotation direction RD of the fluid flowgenerator 2. The sub-path 13Sα has a part where the fluid flow directionis switched from the rotation direction RD of the fluid flow generator 2to the opposite direction. In the heatsink 1α of the first variation,one Y-shaped fin 11bα is disposed, which is different from theembodiment described above. The Y-shaped fin 11bα disposed over thefirst region R1 and the fourth region R4 separates the sub-path 13Sα andthe auxiliary path 13Aα.

FIG. 13 is a diagram illustrating details of the main path 13Mα in theheatsink 1α of the first variation. As illustrated in FIG. 13, a part ofthe main paths 13Mα has a first branch section 1341α constituting abranching point with a first fluid path 13aα, and a first joiningsection 1351α constituting a joining point with a second fluid path 13bαon downstream of the first branch section 1341α.

Note that in the first variation, only one of long distance paths 13LDαpassing through the fourth region R4, the third region R3, the secondregion R2, and the first region R1 has the first branch section 1341αand the first joining section 1351α. Further in the first variation,there is no main path 13Mα having a second branch section on downstreamof the first joining section 1351α. Further in the first variation,there is no main path 13Mα having a second joining section for joiningthe first fluid path 13 aα that has branched at the first branch section1341α.

As to the inlets 131α and the outlets 132α that are shared among theplurality of fluid paths 13α, the number is each counted as one. In thiscase, in the long distance path 13LDα in the first variation, the numberof the outlets 132α and that of the inlets 131α are the same six. Notethat the long distance paths 13LDα are the fluid path 13α passingthrough all the four regions R1 to R4, and the fluid path 13α passingthrough the third region R3, the second region R2, and the first regionR1.

In the first variation illustrated in FIG. 13, the long distance path13LDa is constituted using a long distance flow passage 121α extendingover the second region R2 and the third region R3. An upstream end ofthe long distance flow passage 121α may be positioned on a boundarybetween the third region R3 and the fourth region R4, or positioned inthe fourth region R4, or positioned in the third region R3. A downstreamend of the long distance flow passage 121α is positioned in the firstregion R1.

In a plan view from above, a plurality of the long distance flowpassages 121α are arranged in a direction separating from theintersection CP. Among the plurality of long distance flow passages121α, an outermost long distance flow passage 121 aα positioned at thefarthest position from the intersection CP in the second region R2 has ajoining section 135 aα for joining another flow passage 12α in at leastone of the second region R2 and the third region R3. In this variation,in details, the outermost long distance flow passage 121 aα has thejoining section 135 aα in the third region R3. As the joining section135 aα is disposed, stagnation of fluid flow can be prevented. Note thatthe similar joining section 135 a (see FIG. 8) is disposed also in theembodiment described above.

(3-2. Second Variation)

FIG. 14 is a plan view of a heatsink 1β of a second variation. FIG. 14illustrates the heatsink 1β viewed from above. Similarly to theembodiment described above, the heatsink 1β of the second variation alsohas fins 11β for defining a plurality of flow passages 12β on a topsurface 10 aβ of a main body section 10β. A plurality of fluid paths 13βare obtained from the plurality of flow passages 12β. The plurality offluid paths 13β are classified into main paths 13Mβ, sub-paths 13Sβ, andauxiliary paths 13Aβ. A plurality of the main paths 13Mβ, a plurality ofthe sub-paths 13Sβ, and a plurality of the auxiliary paths 13Aβ aredisposed. Note that only some of the plurality of fluid paths 13β areshown by thick lines in FIG. 14.

Also in the second variation, the fluid flows in the same direction asthe rotation direction RD of the fluid flow generator 2 in the main path13Mβ. The sub-path 13Sβ has a part where the fluid flow direction isswitched from the rotation direction RD of the fluid flow generator 2 tothe opposite direction. Also in the second variation, similarly to thefirst variation, there is one Y-shaped fin 11 bβ for separating thesub-path 13Sβ and the auxiliary path 13Aβ.

FIG. 15 is a diagram illustrating details of the main path 13Mβ in theheatsink 1β of the second variation. As illustrated in FIG. 15, a partof the main paths 13Mβ has a first branch section 1341β constituting abranching point with a first fluid path 13 aβ, and a first joiningsection 1351β constituting a joining point with a second fluid path 13bβ on downstream of the first branch section 1341β.

Note that in the second variation, only one of long distance paths 13LDβpassing through the fourth region R4, the third region R3, the secondregion R2, and the first region R1 has the first branch section 1341βand the first joining section 1351β. In addition, in the secondvariation, there is no main path 13Mβ having a second branch section ondownstream of the first joining section 1351β.

In the second variation, the main path 13Mβ having the first branchsection 1341β and the first joining section 1351β has a second joiningsection 1352β for joining the first fluid path 13 aβ that has branchedat the first branch section 1341β. In the second variation, there is amain path 13Mβ having a third branch section 1343 for branching thefluid path 13. There is no joining section to be a joining point of thefluid before and after the third branch section 1343. The main path 13Mβhaving the third branch section 1343 is a short distance path 13SDβ thatpasses through only the second region R2 and the first region R1. In theshort distance path 13SDβ, it is easy to dispose the branch sectionwithout disposing the joining section, because fluid stagnation occursless easily than the long distance path 13LDβ.

As to the inlet 131β and the outlet 132β shared among the plurality offluid paths 13β, the number is each counted as one. In this case, in thesecond variation, the number of the outlets 132β is smaller than that ofthe inlets 131β in the long distance path 13LDβ. Specifically, thenumber of the outlets 132β is four, and the number of the inlets 131β isfive. Therefore in the long distance path 13LDβ, unnecessary increase ofbranching of the fluid path 13β is prevented, and stagnation of fluidflow can be prevented.

Note that also in the second variation illustrated in FIG. 15, anoutermost long distance flow passage 121 aβ has joining sections 135 aβand 135 bβ. Specifically, the outermost long distance flow passage 121aβ has the joining sections 135 aβ and 135 bβ for joining another flowpassage in the second region R2 and the third region R3.

<4. Points to Consider>

Various technical features disclosed in this specification can bemodified variously without deviating from the spirit of the technicalcreation. In addition, the plurality of embodiments and variationsdisclosed in this specification may be combined to the possible extentfor implementation.

INDUSTRIAL APPLICABILITY

The present invention can be applied to cooling devices that are usedfor in-vehicle devices, home appliances, office machines, and the like,for example.

LIST OF REFERENCE SIGNS

1, 1α, 1β heatsink

2 fluid flow generator

10, 10α, 10β main body section

11, 11α, 11β fin

12, 12α, 12β flow passage

13, 13α, 13β fluid path

13 a, 13 aα, 13 aβ first fluid path

13 b, 13 bα, 13 bβ second fluid path

13LD, 13LDα, 13LDβ long distance path

13M, 13Mα, 13Mβ main path

13S, 13Sα, 13Sβ sub-path

100 cooling device

101 cooled body housing section

131, 131α, 131β inlet

132, 132α, 132β outlet

133 sub-path joining section

1341, 1341α, 1341β first branch section

1342 second branch section

1351, 1351α, 1351β first joining section

1352, 1352β second joining section

C central axis

CP intersection

R1 first region

R2 second region

R3 third region

R4 fourth region

RD rotation direction

1. A heatsink to be used with a fluid flow generator that rotates abouta central axis extending vertically to generate a flow of fluid, theheatsink comprising: a main body section having a top surface facing thefluid flow generator in a vertical direction; and fins that extendupward from the top surface so as to define a plurality of flowpassages, wherein four regions defined by an X axis and a Y axis, whichcross each other at an intersection between the central axis and the topsurface and extend in an extending direction of the top surface, arereferred to as a first region, a second region, a third region, and afourth region, in order in the opposite direction to a rotationdirection of the fluid flow generator, in a plan view from above, theplurality of flow passages form a plurality of fluid paths, each ofwhich has an inlet disposed in at least one of the four regions for thefluid discharged from the fluid flow generator to flow in and an outletdisposed in the first region, and a fluid flow direction changes at anacute angle in a middle in at least one of the fluid paths having theinlet in the fourth region.
 2. The heatsink according to claim 1,wherein at least some of the plurality of fluid paths are classifiedinto main paths in which the fluid flows in the same direction as therotation direction of the fluid flow generator, and sub-paths having apart where the fluid flow direction is switched at an acute angle fromthe rotation direction of the fluid flow generator to the oppositedirection.
 3. The heatsink according to claim 2, wherein the main pathsinclude at least one of the fluid paths having the inlet in the thirdregion.
 4. The heatsink according to claim 2, wherein the sub-pathsinclude at least one of the fluid paths having the inlet in the firstregion, in addition to at least one of the fluid paths having the inletin the fourth region.
 5. The heatsink according to claim 2, wherein atleast some of the sub-paths have a sub-path joining section for joininganother one of the sub-paths.
 6. The heatsink according to claim 1,wherein the fins include a Y-shaped fin.
 7. The heatsink according toclaim 6, wherein the Y-shaped fin has a part extending linearly to theoutlet in the first region.
 8. The heatsink according to claim 1,wherein the main body section has a cooled body housing section forhousing a cooled body on its underside.
 9. A cooling device comprising:the heatsink according to claim 1; and the fluid flow generator.
 10. Thecooling device according to claim 9, wherein the fluid is air, and thefluid flow generator is a centrifugal fan that intakes air from the topand discharges the air in a direction perpendicular to a verticaldirection.